So my taurus starts to misfire the other day. The infamous blink CEL. I drove it right home so as to not damage the cat. The car is throwing a P0304 code. So here is the laundry list of things I have checked.
Change all the plugs.
Misted the wires. (no light show)
Change 4 w/ another wire. (even though it sparked when grounded to exhaust mani)
Replaced the coil pack.
Replaced the fuel injector on number 4.
The injector has power and ground according to my meter.
I can hear the injector firing when I plug it in.
Check compression across the 4-5-6 cylinders. They are within 10 percent.
I don't have a leak down tester so I have not done that.
Checked for vacuum leaks using the old carb cleaner method. Two cans later still no leaks.
The TPS, MAF, and O2 Sensor voltage is within range.
Plug four does foul if I let the car run. If I swap it to 5 or 6 it will clean up.
open to suggestions
99 Vulcan P0304 code 
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